Recently, from standpoint of saving natural sources and energy, small sizings and high efficiency of electromagnetic or electronic parts have been demanded, and soft magnetic property, especially Si steel sheets having excellent iron loss have been also required. It is known that soft magnetic properties of Si steel sheets are improved with increasing of addition of Si and exhibit the maximum permeability at about 6.5 wt %, and since natural electric resistance is high, the iron loss is made small. In this kind of steel sheets, if the Si content is less than 4.0 wt %, workability is abruptly worsened, and therefore it has been impossible to produce high Si steel sheets in industrial scales by the rolling process, but it has been found that the warm rolling could be performed on the thin steel sheets through studies.
However, ordinarily used rolling facilities could not secure bending deformation of the coil or temperatures of the materials, and are difficult to roll the high Si steel sheets. For example, Japanese Patent Application Laid-Open No.135,407/86 proposed a facility protecting from an uncoiling reel to first rolling stands with a warming wall, but this facility could not prevent cracks by bending at the deflector rolls or by rolling.
This invention has been developed in view of problems involved with the prior art, and is to provide a warm rolling facility which may carry out the rolling efficiently without causing cracks in thin steel sheets with less workability.